Dogs (Canis lupus familiaris) are susceptible to the Kanizsa’s triangle illusion

Abstract

The ability to complete partially missing contours is widespread across the animal kingdom, but whether this extends to dogs is still unknown. To address this gap in knowledge, we assessed dogs’ susceptibility to one of the most common contour illusions, the Kanizsa’s triangle. Six dogs were trained to discriminate a triangle from other geometrical figures using a two-alternative conditioned discrimination task. Once the learning criterion was reached, dogs were presented with the Kanizsa’s triangle and a control stimulus, where inducers were rotated around their centre, so as to disrupt what would be perceived as a triangle by a human observer. As a group, dogs chose the illusory triangle significantly more often than control stimuli. At the individual level, susceptibility to the illusion was shown by five out of six dogs. This is the first study where dogs as a group show susceptibility to a visual illusion in the same manner as humans. Moreover, the analyses revealed a negative effect of age on susceptibility, an effect that was also found in humans. Altogether, this suggests that the underling perceptual mechanisms are similar between dogs and humans, and in sharp contrast with other categories of visual illusions to which the susceptibility of dogs has been previously assessed.

Visual snake aversion in Octodon degus and C57BL/6 mice

Abstract

Phobia against spiders or snakes is common in humans, and similar phobia-like behaviors have been observed in non-human animals. Visual images of snakes elicit phobia in humans, but sensory modalities that cause snake aversion in non-human animals are not well examined. In this study, we examined visually induced snake aversion in two rodent species. Using a three-compartment experimental chamber, reactions to images of snakes were compared between the diurnal precocious rodent Octodon degus and nocturnal laboratory mice. The snakes whose images were presented do not live in the original habitats of degus or mice. Snake aversion was assessed by presenting snake vs. no-image, snake vs. flower, snake vs. degu, and snake vs. mouse images. The time spent in a compartment with the snake image and with the non-snake images were measured. Degus avoided images of snakes in every tests. In contrast, mice did not display snake aversion. Degus are diurnal animals, i.e., visual information is important for their survival. Since mice are nocturnal, visual information is less important for survival. Such behavioral differences in the two species may explain the difference in visually induced aversion to snakes. A principal component analysis of the stimulus images suggests that elementary cues, such as color, do not explain the differences in the species’ aversion to snakes. Finally, snake aversion in degus suggests that aversion is innate, since the animals were born and raised in a laboratory.

Kea (Nestor notabilis) show flexibility and individuality in within-session reversal learning tasks

Abstract

The midsession reversal paradigm confronts an animal with a two-choice discrimination task where the reward contingencies are reversed at the midpoint of the session. Species react to the reversal with either win-stay/lose-shift, using local information of reinforcement, or reversal estimation, using global information, e.g. time, to estimate the point of reversal. Besides pigeons, only mammalian species were tested in this paradigm so far and analyses were conducted on pooled data, not considering possible individually different responses. We tested twelve kea parrots with a 40-trial midsession reversal test and additional shifted reversal tests with a variable point of reversal. Birds were tested in two groups on a touchscreen, with the discrimination task having either only visual or additional spatial information. We used Generalized Linear Mixed Models to control for individual differences when analysing the data. Our results demonstrate that kea can use win-stay/lose-shift independently of local information. The predictors group, session, and trial number as well as their interactions had a significant influence on the response. Furthermore, we discovered notable individual differences not only between birds but also between sessions of individual birds, including the ability to quite accurately estimate the reversal position in alternation to win-stay/lose-shift. Our findings of the kea’s quick and flexible responses contribute to the knowledge of diversity in avian cognitive abilities and emphasize the need to consider individuality as well as the limitation of pooling the data when analysing midsession reversal data.

The effect of dimensional reinforcement prediction on discrimination of compound visual stimuli by pigeons

Abstract

We trained eight pigeons (Columba livia) on a stagewise go/no-go visual discrimination task. A total of 16 visual stimuli were created from all possible combinations of four binary dimensions: brightness (dark/bright), size (large/small), line orientation (vertical/horizontal), and shape (circle/square). In the first stage, we presented S + and four S– stimuli: sharing one (brightness), two (brightness and orientation), three (brightness, orientation, and size), or no dimensional values with S + . In the second stage, all 16 stimuli were presented. In the first stage, stimulus discrimination was controlled by the number of dimensional disparities between non-rewarded stimuli and a rewarded one rather than by stimulus dimensional salience, whereas at the beginning of the second stage, pigeon behaviour was controlled mainly by dimensional reinforcement expectancy learned in the first stage. At the beginning of the second stage, pigeons correctly rejected 6–8 of 11 new added S- stimuli. A significant inverse correlation between the number of S– stimuli sharing dimension values with S + in the first stage and the dimensional discrimination ratios at the beginning of the second stage was found.

An initial exploration of mirror behaviour in the ferret, Mustela putorius furo

Abstract

Responses to mirrors vary in non-human animals. Many species respond socially to mirrors with relatively few species demonstrating self-recognition in mirrors. In this study, we investigated the responses of ferrets to mirrors. Six adult ferrets (3 males, 3 females, all over a year old) were exposed to mirrors and their responses were investigated over three experimental conditions (baseline, mirror preference, mark test) in a repeated measures design. Upon initial presentation, the ferrets showed more approach and sniffing behaviour toward the mirror than the non-reflective surface. The ferrets also showed a preference for the mirror and spent more time in close proximity to the mirror than the non-reflective surface. In the mirror mark test, the ferrets showed more approach, sniffing and self-exploration behaviour when they were marked and presented with the mirror compared to when they were marked and presented with the non-reflective surface, or when they were sham-marked and presented with either surface. Our findings are suggestive that ferrets show interest in mirrors and that further study exploring the responses of ferrets to mirrors is warranted.

The effects of food limitation on behavior, corticosterone, and the use of social information in the red crossbill (Loxia curvirostra)

Abstract

Meeting metabolic demands through foraging is a basic animal need that drives the evolution of foraging adaptations. The use of social information is one adaptation that could improve foraging success and fitness if it helps animals locate food when conditions are challenging. It is unknown if food limitation—or the glucocorticoid hormones that are often released when food is limited—can influence the extent to which animals use social information or their ability to learn novel foraging techniques. We explored the effects of limited access to food on activity levels, corticosterone secretion, and social information use in red crossbills, a highly social songbird species adapted to cope with high degrees of resource unpredictability. Using an observer/demonstrator paradigm, food limited or well fed observers were allowed to watch demonstrators solve a novel feeding puzzle before being allowed to attempt the puzzle themselves across repeated trials. Our findings suggest that food limitation transiently increased activity levels but did not result in long-term elevations of corticosterone and did not increase the speed at which red crossbills utilized social information to solve the novel foraging task. However, food limitation may have increased the value of using socially acquired information, as foraging technique performance improved faster in food limited birds relative to controls. Social learning was further demonstrated by the red crossbills in this study when naïve observers overwhelmingly learned a socially-demonstrated task over an undemonstrated task when tested on a two-task foraging board.

Trace conditioning as a test for animal consciousness: a new approach

Abstract

Trace conditioning involves the pairing of a neutral conditioned stimulus (CS), followed by a short interval with a motivationally significant unconditioned stimulus (UCS). Recently, trace conditioning has been proposed as a test for animal consciousness due to its correlation in humans with subjective report of the CS–UCS connection. We argue that the distractor task in the Clark and Squire (1998) study on trace conditioning has been overlooked. Attentional inhibition played a crucial role in disrupting trace conditioning and awareness of the CS–UCS contingency in the human participants of that study. These results may be understood within the framework of the Temporal Representation Theory that asserts consciousness serves the function of selecting information into a representation of the present moment. While neither sufficient nor necessary, attentional processes are the primary means to select stimuli for consciousness. Consciousness and attention are both needed by an animal capable of flexible behavioral response. Consciousness keeps track of the current situation; attention amplifies task-relevant stimuli and inhibits irrelevant stimuli. In light of these joint functions, we hypothesize that the failure to trace condition under distraction in an organism known to successfully trace condition otherwise can be one of several tests that indicates animal consciousness. Successful trace conditioning is widespread and by itself does not indicate consciousness.

Emergence of complex dynamics of choice due to repeated exposures to extinction learning

Abstract

Extinction learning, the process of ceasing an acquired behavior in response to altered reinforcement contingencies, is not only essential for survival in a changing environment, but also plays a fundamental role in the treatment of pathological behaviors. During therapy and other forms of training involving extinction, subjects are typically exposed to several sessions with a similar structure. The effects of this repeated exposure are not well understood. Here, we studied the behavior of pigeons across several sessions of a discrimination-learning task in context A, extinction in context B, and a return to context A to test the context-dependent return of the learned responses (ABA renewal). By focusing on individual learning curves across animals, we uncovered a session-dependent variability of behavior: (1) during extinction, pigeons preferred the unrewarded alternative choice in one-third of the sessions, predominantly during the first one. (2) In later sessions, abrupt transitions of behavior at the onset of context B emerged, and (3) the renewal effect decayed as sessions progressed. We show that the observed results can be parsimoniously accounted for by a computational model based only on associative learning between stimuli and actions. Our work thus demonstrates the critical importance of studying the trial-by-trial dynamics of learning in individual sessions, and the power of “simple” associative learning processes.

Long-term stability of vocal individuality cues in a territorial and monogamous seabird

Abstract

The stability of individual acoustic features is fundamental in social species, and more importantly in monogamous and territorial species, showing long-term fidelity both to the partner and the breeding site. In this study, the stability over time of two discrete vocal types was investigated in the African penguin (Spheniscus demersus), a monogamous and territorial seabird. Contact calls and ecstatic display songs were recorded from an ex situ colony in 2017 and in 2020. For each vocalisation, we measured 14 spectral and temporal acoustic parameters related to both source and filter components. Two separate leave-one-out cross-validated Discriminant Function Analyses (DFA) were then performed, generating the discriminant functions from the vocalisations collected in 2017 to classify those recorded in 2020. The DFA correctly classified 62% of the contact calls (10 subjects) and 80.9% of the ecstatic display songs (seven subjects) according to the correct emitter, showing that acoustic cues to individuality encoded in both vocal types remained unchanged over four consecutive breeding seasons. We suggest that, in this monogamous and territorial bird species, individual acoustic stability could be selected for to identify groupmates and neighbours over the years and to help couples to reunite in consecutive breeding seasons, increasing individual fitness.

Learning about construction behaviour from observing an artefact: can experience with conspecifics aid in artefact recognition?

Abstract

Observation of or interaction with the enduring products of behaviour, called ‘social artefacts’ (e.g. an abandoned nest) is a potential source of social information. To learn from an artefact, that artefact needs to be recognized as the product of a behaviour that can provide relevant information (i.e. the artefact should be recognized as a nest). We used zebra finches (Taeniopygia guttata) to experimentally test whether observing a conspecific using a nest facilitates recognition of a future artefact as a source of social information. We manipulated the opportunity to form an association between a conspecific and their nest: half the subjects observed a pair of birds incubating eggs in a nest, the control subjects did not get this opportunity. Then, subjects observed an artefact made of their non-preferred colour and finally were allowed to build a nest. We predicted that the subjects given the opportunity to associate a nest with conspecifics would copy the colour of the artefact (i.e. use social information). We found that subjects who had the opportunity to learn what a nest is used social information obtained from the artefact by increasing their use of the artefact-material colour after artefact observation, while control birds did not. These data suggest that forming an association between conspecifics and their nest facilitates recognition of an artefact as a nest affecting how first-time builders use social information. This finding is important because it demonstrates that social learning is not limited to observing behaviour, but rather inferring behaviour from an artefact.